Today, I released a minor version update to Statistical PERT® Normal Edition. Version 2.1 adds a new worksheet, **SPERT Normal® (Mixed entry). **This new worksheet offers estimators a very flexible way to enter uncertainties into a SPERT worksheet. Using this worksheet, estimators can very easily create three-point estimates with little effort using heuristics to generate the minimum and maximum extreme values for each uncertainty, and then estimators can selectively choose to change those auto-created values with row-level, exception-based values.

In this worksheet, estimators have three ways to create the necessary 3-point estimate that every Statistical PERT calculation requires. Firstly, two global heuristics are specified above the **Minimum** and **Maximum** column headings. The **Minimum **heuristic will reduce the value entered in the **Most Likely **column by a percentage value. Similarly, the **Maximum **heuristic will increase the value in the **Most Likely **column by a percentage value. These two heuristics will affect all entered uncertainties in this particular worksheet.

Estimators can, at the row level, override any globally-derived Minimum and Maximum point-estimates in one of two ways, One way to do that is specify a row-level heuristic by selecting a percentage value in either the **Min % **or **Max %** column. These percentages only affect a single row. They both either reduce or increase the value in the **Most Likely** column, just like the global heuristics do, but only at a single row level. The other way estimators can override a calculated minimum and/or maximum point-estimate is to manually enter a value in the **Min point** and/or **Max point** column. Manually entering a minimum and/or maximum point-estimate will always override any point-estimate value that is a calculated result.

**Most Likely **point-estimates must always be manually entered by an estimator; there is no built-in way to calculate a Most Likely point-estimate. But once a Most Likely point-estimate is entered, an estimator can either use a global or row-level heuristic to create the minimum and/or maximum point-estimates for each uncertainty, or estimators can continue to manually enter specific values for those point-estimates.

While this new worksheet may look a little more complex because of the extra columns, using it is still very simple. This simply makes it easier for an estimator to create exception-based point-estimates when dealing with a large number of uncertainties in the SPERT worksheet.

The example workbook includes examples of all three ways to create minimum and maximum point-estimates. The first three rows (ID 1, 2 and 3) have minimum and maximum point-estimates that are created from the global heuristics. For these three uncertainties, minimum point-estimates are 50% less than the most likely point-estimate, and maximum point-estimates are 100% greater than the most likely point-estimate.

ID 4, however, overrides the global heuristic with two row-level heuristics: the minimum point-estimate is only 10% less than the most likely outcome, and the maximum point-estimate is only 50% greater.

ID 5 uses a row-level heuristic to reduce the most likely outcome by 25%, but the maximum point-estimate (160) is manually entered and overrides the global heuristic for creating maximum point-estimates.

ID 6 specifies a value of 40 for the minimum point-estimate, which overrides the global heuristic for creating minimum point-estimates, and the maximum point-estimate of 200 is manually entered, too.

ID 7 specifies 80 for the minimum point-estimate, but uses a row-level heuristic to create a maximum point-estimate that is 75% greater than ID 7’s most likely value.

So, the new **Mixed entry **worksheet offers estimators the greatest amount of flexibility to create 3-point estimates in the easiest way possible. Download Version 2.1 now!